Conventional dishwashers include a main pump assembly for circulating water through one or more spray arm assemblies, typically an upper and lower spray arm assembly. The spray arm assemblies have arms that extend radially from a central hub, with nozzles or ports provided along the arm for directing the water from the arms at a defined spray pattern. The water pressure and angular orientation of the discharge nozzles generate a rotational torque that causes the arms and hub to rotate.
Typically, the effectiveness of the dishwasher is a function of a number of parameters such as solvent (e.g., water) flow rate, solvent coverage, temperature of the solvent, chemical energy, nozzle geometry, nozzle size, rotational speed (generally expressed in units of revolutions per minute, or “RPM”) of spray arm and jet force. The wash cycle of the dishwasher operation requires sufficient solvent flow rate, coverage, thermal and chemical energy. Further, the rinse cycle requires coverage and an amount of solvent that is sufficient for removing detergent and excess food particles from the dishes. Thus, the rinse cycle requires a relatively lower solvent flow rate as compared to the wash cycle for maintaining the same coverage.
In a conventional dishwasher, a single hydraulic system is employed for all modes of operation of the dishwasher cycle such as pre-wash, wash, and rinse cycles. Further, the solvent flow rate and spray coverage/pattern is the same for all these modes of operation. As a result, such dishwashers utilize huge amounts of water and energy for washing the dishes.
Accordingly, a need exists for providing a dishwasher that utilizes substantially lower amounts of water and energy for washing the dishes by tailoring the solvent flow rate (pressure) and spray coverage/pattern to the various operational cycles of the dishwasher.